title: Seasonal changes in gonadal steroids of a monogamous versus a polyandrous shorebird.
abstract: We examined the relationship between circulating levels of gonadal steroids (testosterone, progesterone, and estradiol) and breeding behavior in semipalmated sandpipers (Calidris pusilla) and red-necked phalaropes (Phalaropus lobatus) breeding sympatrically at La Pérouse Bay, 40 km east of Churchill, Manitoba. Semipalmated sandpipers are territorial and monogamous. Both parents incubate equally. Red-necked phalaropes are nonterritorial and polyandrous. Only male phalaropes care for eggs and young. Gonadal steroid hormone profiles were not reversed in the sex-role-reversed species. There was little difference in testosterone profiles between males of the territorial and nonterritorial species.
authors.affiliation: Department of Biology, University of North Dakota, Grand Forks 58202.
authors.forename: C L
authors.initials: CL
authors.lastname: Gratto-Trevor
authors.forename: A J
authors.initials: AJ
authors.lastname: Fivizzani
authors.forename: L W
authors.initials: LW
authors.lastname: Oring
authors.forename: F
authors.initials: F
authors.lastname: Cooke
mesh_terms: D000818:Animals; D001717:Birds / Q000097:blood*; D004958:Estradiol / Q000097:blood*; D005260:Female; D008297:Male; D011374:Progesterone / Q000097:blood*; D012621:Seasons; D012737:Sex Factors; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013045:Species Specificity; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone; D011374:Progesterone; D004958:Estradiol